3. Rearrange stat totals, or add some like X and Y did to some mons.
Yeah, its nice that some mons got an increase of like 10 in some stat or another last time, but the power creep has been so much bigger than that (especially in terms of move sets) it's really not enough, especially on the gen 1 monsters. I think there's only like 13 gen 6 mons in the bottom 200, almost entirely first forms, but nearly 30 of them in the top 200… (And the top 100 are almost all final form starts, legends or dragons).
Especially when stats were distributed weird in the first two gens, before the special/physical split and when speed affected criticals.
Megas have alleviated that some, but in the opposite direction, sending everything into broken ability legendary stats categories.